1. Field of the Invention
This invention relates generally to a brush device for a small electric motor, and more specifically to a brush device for a small electric motor wherein a strip of thin brush material integrally forms to a commutator slide, a brush base, a terminal portion and a reinforcing piece which is provided on the brush base portion of the brush strip as a means for aiding in the fixing of the brush device to a motor case cover.
2. Description of the Prior Art
A brush device of the conventional type for a small electric motor usually has a brush device integrally constructed so as to include a commutator slide, a brush base and a terminal portion. Conventionally the integrally constructed brush device is fixed to a motor case cover by three-point support at the center and both sides of the brush base which is inserted into a terminal insert hole provided on the motor case cover. The brush device of this type, however, tends to come out of the terminal insert hole since the brush device is fixed to the motor case cover simply by bending and inserting the brush device into the terminal insert hole, utilizing the resiliency of the material. To prevent the brush device from coming out of the terminal insert hole and to securely fix the brush device to the motor case cover, it has been suggested in the prior art that a cut and raised piece be provided on the brush base to bite into the inside wall of the terminal insert hole.
More recently, however, various means have been devised to minimize friction loss between the brush device and the commutator and to prevent unwanted resonance due to the revolution of the motor by reducing the natural frequency of the brush device. In such a case, a resilient electrically conductive material is naturally selected for the brush, but the thickness of such a brush material has to be as thin as 0.08 mm or less. However, the thinner the brush material becomes, the less toughness there is in the brush itself. Thus, it becomes difficult to effect a three-point support for the brush, using the resiliency of the brush material. As a means for solving this problem, reinforcement of the brush device by increasing the thickness of the brush base, compared with that of the commutator slide portion has been contemplated that this would make the manufacturing process of brush more complicated.
This invention is intended to securely fix the brush device to the motor case cover and to reinforce the brush base by forming the brush base into a simple shape.